This invention relates to a power operating system for a vehicle liftgate that is pivotally attached to a vehicle compartment for pivotal movement about a generally horizontal hinge axis and more particularly to a power operating system that will move a liftgate from a closed position to a fully open position and from an open position to a fully closed position.
Utility vehicles and vans with liftgates that are hinged at the top about a generally horizontal axis are used by large numbers of people today. Some of these liftgates are large and heavy. Their size and weight make some liftgates difficult to open and close. Some of the liftgates are also a great distance above the ground when they are fully opened. Their height above the ground makes them very difficult for some people to close. For these and other reasons many people would like to have a power operating system for opening and closing the liftgate.
A number of different liftgate openers have been tried in recent years. Some of these liftgate openers have a single cable that opens and closes a liftgate in connection with a counterbalance system, such as a gas spring counterbalance system. Liftgates with a single cable opener and closer are generally trunk lids that are lightweight and have a relatively small range of movement.
Gas spring output varies with temperature. This complicates power liftgate systems that rely on gas springs to open the liftgate. The gas spring or springs must be strong enough to open the liftgate on the coldest day (xe2x88x9240xc2x0 C.). This results in gas springs that increase closing resistance substantially on the hottest day (80xc2x0 C.). Therefore a very large electric motor must be used to close the liftgate.
Liftgates that have two or more gas springs for a counter balance system are common. These gas springs generally occupy a position in which their axis is substantially parallel to the liftgate so that the gas springs are hidden when the liftgate is closed. In this closed position the moment arm of the gas springs is quite small. With such systems the lift gate may move about one-third of their total travel range before the gas cylinders exert sufficient force to open a liftgate further without the application of an independent lifting force. There are even some systems in which the gas springs pass over center and bias a liftgate toward a closed position when the liftgate is closed. With these self-closing systems a liftgate may need to be more than one-third open before the gas springs will open the liftgate further.
The force required to hold a liftgate in a given position along its path of movement from a closed position to a fully open position varies substantially in some liftgate opening systems. A power liftgate closer must exert sufficient force to hold a liftgate in any given position along the path of movement, plus the force to overcome friction, and plus the force required to accelerate the liftgate during liftgate closing. If the total force exerted by the liftgate power closure varies substantially from one position between fully opened and closed to another position between fully opened and closed, it may be difficult for the control system to detect an obstruction and stop the liftgate without incurring damage to the vehicle or to the object that obstructs the liftgate.
The object of the invention is to provide an improved vehicle liftgate power operating system.
A feature of the invention is that the vehicle liftgate power operating system can move the liftgate from a closed position to a fully opened position as well as from an open position to a fully closed position.
Another feature of the invention is that the liftgate power operating system allows the liftgate to be moved manually when an efficient gear train is selected.
Another feature of the invention is that power operating system can be stopped at any point to hold the liftgate in any intermediate position without any need for a brake, detent or the like.
Still another feature of the invention is that the drive unit of the liftgate power operating system has a segmented drive linkage attached to the liftgate that is guided by a track that is preferably shaped to hug the interior roof structure and thus minimize intrusion into the cargo area of the vehicle and maximize the unobstructed load height at the liftgate opening.
Yet another feature of the invention is that the liftgate power operating system preferably has a moveable link arm attached to the liftgate that is preferably shaped and guided to move concentrically with respect to the hinge axis of the liftgate so that the moveable link arm can be sealed easily and/or located exit outside the liftgate perimeter seal.
Still yet another feature of the invention is that the liftgate power operating system has a flexible drive member, preferably a power roller chain that is routed in a track of desired shape easily.
Still yet another feature of the invention is that the power operating system can be used in conjunction with a counterbalance system.
These and other objects, features and advantages of the invention will become more apparent from the following description of a preferred embodiment taken in conjunction with the accompanying drawing.